Steam engine

ABSTRACT

A steam engine has a base with end plates journalling a driven shaft which supports a main rotor including a pair of spaced helical gears of opposite hand. A series of spaced axles are arranged around said shaft and journalled on said plates. A chambering rotor includes a pair of spaced helicoid gears of opposite hand mounted on each axle in mesh with said first gears. An elongated bonnet is adjacent each chambering rotor and secured to said end plates. Said bonnet has a pair of intersecting elongated transversely arcuate surfaces adjacent said rotors providing a close running fit with the peripheries of the mating rotors throughout their length, and extending circumferentially of the central longitudinal plane wherein, the respective peripheries of both rotors coincide. Said bonnet seals off the respective expansion chambers defined between and along the adjacent intermeshing rotors. A bulkhead projects from each arcuate surface and nests with a running fit within the annular space between the inner ends of the helical gears of the chambering rotor and main rotor. Each bulkhead terminates in a tang chamferred upon its opposite sides defining a knife edge. An arcuate steam duct, connected to a source of steam under pressure, is mounted on each bonnet, extends around the chambering rotor and is nested with a running fit between the inner ends of its helical gears and the helical gears of said main rotor. The outlet end of the steam duct receives said knife edge so that steam delivered thereto is deflected from both sides thereof into the ends of the progressively developing expansion chambers defined by the intermeshing helical gears.

United States Patent [191 Grenier Dec. 16, 1975 STEAM ENGINE [76] Inventor: Bernard J. Grenier, Garden, Mich.

[22] Filed: Nov. 25, 1974 [21] Appl. No.: 527,021

Primary ExaminerC. J. Husar Assistant Examiner--Leonard Smith Attorney, Agent, or Firm-Cullen, Settle, Sloman & Cantor [57] ABSTRACT A steam engine has a base with end plates journalling a driven shaft which supports a main rotor including a pair of spaced helical gears of opposite hand. A series of spaced axles are arranged around said shaft and journalled on said plates. A chambering rotor includes a pair of spaced helicoid gears of opposite hand mounted on each axle in mesh with said first gears. An elongated bonnet is adjacent each chambering rotor and secured to said end plates. Said bonnet has a pair of intersecting elongated transversely arcuate surfaces adjacent said rotors providing a close running fit with the peripheries of the mating rotors throughout their length, and extending circumferentially of the central longitudinal plane wherein, the respective peripheries of both rotors coincide. Said bonnet seals off the respective expansion chambers defined between and along the adjacent intermeshing rotors. A bulkhead projects from each arcuate surface and nests with a running fit within the annular space between the inner ends of the helical gears of the chambering rotor and main rotor. Each bulkhead terminates in a tang chamferred upon its opposite sides defining a knife edge. An arcuate steam duct, connected to a source of steam under pressure, is mounted on each bonnet, extends around the chambering rotor and is nested with a running fit between the inner ends of its helical gears and the helical gears of said main rotor. The outlet end of the steam duct receives said knife edge so that steam delivered thereto is deflected from both sides thereof into the ends of the progressively developing expansion chambers defined by the intermeshing helical gears.

12 Claims, 11 Drawing Figures US, mm Dec. 16, 1975 Sheet10f3 3,926,540

AM RCE U.S. Patent Dec. 16, 1975 Sheet 2 of3 3,926,540

FIG.3

STEAM ENGINE BACKGROUND OF THE INVENTION When two helical gear wheels, of opposite end, are meshed together on parallel axles and rotated, there shall develop between their teeth, on that end where the helices emerge, a never-ending succession of small cavities, which starting from nothing, expand continu ously until they actually cease to exist. If a pair of gear wheels were covered with a close fitting bonnet and a bulkhead were positioned over the end, these cavities should become chambers and when pressurized, should expand to rotate the wheels.

Heretofore, others have considered this possibility such as shown in the United States Patents of Backstrum, US. Pat. No. 572,946 of 1896 and US. Pat. No. 1,247,552 of Lindenberg of 1917.

The reason these disclosures were unworkable was because of the difficulty of actually pressurizing the ex pansion chambers.

Conventional helical gears have two inherent characteristics which prevent this proposed function. The ever present gaps between the convex surfaces of the mating teeth, together with a similar gap between the end of the teeth and the bottom of the tooth space, permit an intolerable amount of blow by.

BRIEF DESCRIPTION OF THE INVENTION It is an object of the present invention to provide an improved steam engine which will substantially eliminate this blow by.

It is another object to provide a bonnet construction in conjunction with the mating rotors and to further so construct the spiral gear teeth making up the helicoids as to establish efficient functional expansion chambers at the point of coincidence between the meshing main gear referred to as the main rotor herein and the series of chambering rotors mounted around said main rotor and in mesh therewith.

It is a further object to provide an improved rotor construction wherein the individual rotor is defined by a series of gear tooth discs of the number one and number two grouping where in the number one grouping, the teeth have larger than normal OD. and smaller than normal root diameters and wherein, in the group two discs, the teeth have smaller than normal O.D.s and larger than normal root diameters.

It is a further object in constructing the rotor to arrange the number one and number two groups alternately along a supporting shaft with means for securing the gear tooth discs together with the teeth of each successive gear tooth disc along the length of the rotor advanced with respect to the proceeding gear teeth a distance approximately the thickness of the gear tooth discs.

It is another object to provide an improved means for delivering steam under pressure from a unit manifold and through suitable steam pipes so as to deliver the steam directly into the expansion chambers at the point of coincidence between the respective meshing rotors.

These and other objects will be seen from the following specification and claims in conjunction with the ap pended drawings.

THE DRAWINGS FIG. 1 is a fragmentary and schematic side elevational view of the present steam engine.

FIG. 2 is a vertical section taken in the direction of arrows 2-2 of FIG. 1.

FIG. 3 is a plan view of one of the chambering rotors of FIG. 1, shown on an increased scale, and assembled with respect to a steam duct and bonnet bulkhead, fragmentarily shown.

FIG. 4 is an end view of the rotor shown in FIG. 3.

FIG. 5 is a top view of the bonnet shown in FIGS. 1 and 2, on an enlarged scale with a portion of the steam duct mounted thereon and fragmentarily shown.

FIG. 6 is a plan view of a group number one gear tooth disc and a corresponding plan view of a group two disc as alternately assembled upon the rotor or axle shafts of FIG. 2.

FIG. 7 is an end elevational view of the group two gear tooth disc.

FIG. 8 is a fragmentary view of an axle with spacing collar forming a part of a chambering rotor shown in FIG. 2.

FIG. 9 is a right end view thereof.

FIG. 10 is a front view of the retaining collar for the series of alternated gear tooth discs defining a rotor.

FIG. 11 is a side view thereof.

It will be understood that the above drawings illustrate merely a preferred embodiment of the invention, and that other embodiments are contemplated within the scope of the claims hereafter set forth.

DETAILED DESCRIPTION OF THE INVENTION The present steam engine requires the pressurizing of the expansible chambers developed between the teeth of two meshing helical gear rotors as they rotate on parallel axes, while a close-fitting contoured bonnet is positioned over the juncture between the rotors and retains the radial pressure and a bulkhead retains the axial pressure.

The present engine is composed of one large double helical rotor whose function is to absorb energy from the steam by forming one side of the expansible chambers and to convert it into rotary motion. This main rotor is surrounded and meshed with a suitable number of smaller double helical chambering rotors whose primary function is to mesh with the main rotor to form the opposite side of the expansible chambers. They, too, absorb energy from the steam which'they transmit back to the main rotor.

Referring to the drawings, FIGS. 1 and 2, the present steam engine includes a base 13 mounting a pair of spaced end plates 15. Driven shaft 17 spans said plates and extends through suitable bearings 19 therein for the mounting of the main rotor 21, FIG. 2. Said main rotor has mounted thereon a pair of spaced helicoid gears 23 of opposite hand in an arrangement of helic oid gears similar to what is shown in FIG. 3 which is illustrative of a chambering rotor of similar construction.

A series of spaced axles 25 span and are joumalled upon said end plates and are arranged around, outwardly of and parallel to said shaft with suitable bearings interposed in said end plates. Each of the axles 25 mount a chambering rotor 27, FIGS. 1, 2 and 3, which includes a pair of spaced helicoid gears 29 of opposite hand.

As shown in FIG. 2, the opposed helicoid gears 23 of the main rotor are in mesh with the corresponding helicoid gears 29 of the respective chambering rotors 27. Expansion chambers 31 are thus defined between the teeth of the opposed registering helicoids where the helices emerge. This expansion chamber 31 is in the nature of a continuous succession of emerging small cavities or chambers which start from nothing and which expand continuously until they actually cease to exist. The numeral 31 of FIG. 2 illustrates the location of the respective expansion chambers determined by the gear teeth of the respective helicoids at their point of coincidence and to which in accordance with the present invention, a stream of pressurized steam is delivered for action upon the walls of said expansion chamber. One wall of the expansion chamber is defined by the adjacent gear teeth from a chambering rotor and the other wall is defined by the adjacent gear teeth from the main rotor.

In the construction of the respective main and chambering rotors, there is provided upon the corresponding shaft or axle 25, FIG. 8, a spacing collar 33. Said collar is secured to said shaft or axle and has arranged around its periphery a circle of spaced threaded bores 35.

Each rotor, whether it be a main rotor or a chambering rotor, includes a plurality of gear tooth discs 37 (number one) and gear tooth discs 39 (number two), FIG. 6, having a respective bore 41 and arranged upon said shaft or axle 25 with the gear tooth discs one and two alternating successively.

Each of the gear tooth discs 37 and 39 have a series of teeth 45 of generaly spur gear shafe defining therebetween the tooth spaces 47.

A suitable retaining collar 49, FIG. 10, having a bore 51 is assembled over the respective shaft or axle 25. A series of bores 53 are formed in a circle around the retaining collar and are adapted to receive a series of elongated screws 55 which project therethrough and through the corresponding bores 43 of the alternated gear tooth discs, and thread into the bores 35 of spacing collar 33 to provide a unit assembly. The general thickness of the individual gear tooth discs is designated in FIG. 7.

Referring to the bracketed drawing, FIG. 6, showing the group one and group two gear tooth discs 37 and 39, the respective teeth of the gear tooth disc number one as at 57 are slightly larger than the normal outside diameter as schematically shown in dash lines. The teeth 59 from the gear tooth disc number two are smaller than the normal CD. as schematically shown. Accordingly, in the construction of a rotor and in the alternate arrangement of the gear tooth discs one and two, between the teeth of adjacent discs there will be steps of a zig-zag form, defining a series of alternately ridges and depressions. These ridges and depressions are adapted for respective cooperating registry with corresponding series of depressions and ridges in the mating gear element of the opposing rotor in operation.

Referring again to FIG. 6, the tooth root 61 is smaller than the normal root diameter schematically shown in disc group number one. However, the tooth root 63 of the number two disc is larger than the normal root diameter.

Accordingly, the tooth spaces at the root thereof are stepped or staggered with alternating rises and depressions and are adapted for corresponding cooperating registry with the opposed undersized or oversized tooth ends of the adjacent rotor.

In the assembly of the respective gear tooth discs number one and number two upon the respective shaft or axle, each of the teeth from the respective discs are successively advanced a step from the next succeeding or adjacent tooth as at 65, FIG. 4. The advancement of 4 the respective discs is equal substantially to the thickness of the individual discs, such as shown in FIG. 7.

Accordingly, the discs so advanced define the respective helix grooves 67, FIG. 3, which are of a zig-zag or step form due to the advancement of the respective teeth of the gear discs. This, thus, provides non-continuous surfaces which bound the walls of the expansion chambers 31 as they develop progressively during simultaneous rotation of the intermeshing main rotor and chambering rotors.

An elongated bonnet 69 is arranged adjacent each chambering rotor 27, spans the end plates 15 and is secured thereto by fasteners 71, FIG. 1. Each bonnet has a first transversely concave running surface 73 in close registry with the gear teeth of the main rotor, and an intersecting elongated transversely concave running surface 75, FIG. 2, adjacent the teeth of the chambering rotor.

As shown in FIG. 5, each of the transversely concave surfaces 73 and 75 have formed therein a series of spaced slots 77 and ridges 79 which are radial of the axis of said bonnet. Said slots and ridges are adapted to cooperatively receive the corresponding raised and lowered tooth ends of the respective rotor as shown at 57 and 59, FIG. 6, during rotation thereof.

The intersecting arcuate surfaces, 73 and 75 of said bonnet, provide a close running fit with the peripheries of both mating rotors throughout their length and extending circumferentially both sides of a central longitudinal plane wherein, the peripheries of both rotors coincide, thence through arcs equal to those spanned by the helices of each rotor. The said bonnets, therefore, seal off the respective expansion chambers 31, defined between and along the adjacent intermeshing chambering rotors and main rotor.

Arcuate bulkheads 81 and 83 of general rectangular shape and cross section are arranged intermediate the ends of the respective bonnet and extend from the corresponding concave surfaces 73 and 75.

These bulkheads are adapted to have a running fit within the annular space between the respective inner ends of the helical gears of the chambering rotor and main rotor, closing off the corresponding expansion chambers 31 on opposite sides of the bulkhead.

The internal arcuate surfaces of the bulkheads 81 and 83 are adapted for registry with the corresponding collars 33 which form a part of the respective rotors. The respective bulkheads 81 and 83 terminate in a tang 85 whose opposite sides are chamferred at 87 at an angle of about 45-55 to define the centrally disposed knife edge or steam diverter 89.

As shown in FIG. 1, steam manifold 93 is connected at 95 to a suitable source of steam under pressure and through a series of separately connected conduits 97 deliver steam to the respective steam ducts 99, FIG. 2, on each of the respective bonnets. Portions of the steam duct 99 are rectangular in cross section with the outlet end 101 thereof receiving and projecting over the knife edge 89 as best shown in FIG. 3.

Accordingly, the respective supply of steam under pressure delivered through the steam duct 99 is diverted or split at the knife edge so as to movelaterally into the respective expansion chambers 31 defined by the mating rotors, upon opposite sides of the knife edge. Each of the steam ducts terminates in a stem 103 with a passage 105 therethrough adapted for communication with the conduit 97 respectively from the said manifold;

Angle members 107 are arranged upon opposite sides of the steam duct stem and secured respectively thereto and to the bonnet 69 by fasteners l09.This anchors the steam duct stems upon the respective bonnets intermediate their ends as best shown in FIG. 2.

As shown in FIG. 3, each of the conduits 97 have a fitting 111 adapted for a juncture with steam pressure manifold 93. a v i As shown in FIG. 1, the drive relation between the chambering, rotors and the main rotor may be secured by the main gear 113 which is secured to the shaft 17 upon the exterior of end plate 15.

Mountedupon the extensions of the respective axles are a series of pinions 1 15 which are in mesh respectively with the main gear 1 13. Thus, a positive drive relation is established between the chambering rotors and mam rotor.

With such an arrangement, it is not necessary for the respective spiral gears of the intermeshing rotors to be actually in direct physical contact with each other and, accordingly, friction would be reduced.

The parallel annular grooves 77 and ridges 79, FIG. 5, formed in the transversely arcuate surfaces of the bonnet are of the proper quantity spacing, width and depth to accommodate the zigzag axial profile of the respective rotors defined by thetwo sets of gear tooth discs number one andnumber two.

In operation, the steam ducts 99 convey the actuating fluid; namely, steam under pressure from manifold 93 to its point of exit at the center line of the meshing rotors where said actuating fluid encounters the knife edged tang 87-89 of the bulkhead 81-83 to divide and impinge against the ends of the helicoids at the respective expansion chambers. This high velocity steam im pinges against the rear running surfaces of the rotor teeth, thereby adding its kinetic energy to the expansion process.

With the use of the group number one and group number two gear tooth discs in forming the respective rotors, there is imparted a zig-zag configuration to the ridge formed by the ends of the respective teeth and, likewise, along the bottom of the tooth spaces. When gears with teeth so formed are meshed together, the longitudinal root gap through which the actuating fluid axial profile otherwise escape is eliminated. The gear discs assembled as shown in FIG. 4 produce a helicoid with a zig-zag profile which travels in the circular grooves formed in the concave running surfaces of the bonnets.

The gear discs, FIG. 6 are stacked on the axle or shaft in such a manner that each succeeding gear disc is advanced circumferentially a distance measured along the pitch circle equal to its thickness. Thus, the teeth and tooth spaces evolve in helices, of about 45 angle, having a stepped configuration. The gear discs on opposite sides of the spacing collar are advanced to form helices or helicoids of opposite hand. These right and left helicoids are staggered circumferentially in relation to each other by one half of one pitch. Companion rotors having teeth arranged in this manner, when meshed together, produce considerable overlapping throughout the length of the helices. This eliminates the gaps between the flanks and faces of the opposing teeth, through which the actuating fluid would otherwise escape. Because the individual gear discs have spur teeth whose pressure surfaces lie parallel to the axle, no end thrusts are developed.

.Having described my invention, reference should now be had to the following claims. I claim:

1. In a steamengine, a base;

a pair of end plates thereon;

a driven shaft spanning and joumalled upon said end plates;

a main rotor including a pair of spaced helicoid gears of opposite handmoun'ted on and secured to said shaft; I

a series of spaced axles spanning and joumalled upon said end plates, arranged around, outwardly of and "parallel to said shaft;

a chambering rotor including a pair of spaced helicoid gears of corresponding opposite hand mounted on and secured to each of said axles;

with the spiral gear teeth of each chambering rotor in v mesh with the corresponding spiral gear teeth of said main rotor;

an elongated bonnet adjacent and parallel to each chambering rotor interposed between and secured to said end plates;

said bonnet having a pair of intersecting elongated transversely arcuate surfaces adjacentsaid rotors providing a close running fit with the peripheries of both mating rotors throughout their length and extending circumferentially both sides of a central longitudinal plane wherein the peripheries of both rotors coincide, thence through arcs equal to those spanned by thehelixes of each rotor;

each bonnet sealing off the respective expansion chambers defined between and along the adjacent intermeshing chambering rotors and main rotor;

an arcuate bulkhead projecting outwardly of each bonnet arcuate surface intermediate its ends nested with a running fit within the annular space between the inner ends of the helical gears of the chambering rotor and main rotor, closing off the corresponding expansion chambers on opposite sides of the bulkhead;

said bulkheads merging at one end and terminating in a tang, chamferred upon its opposite sides defining a knife edge;

an arcuate steam duct mounted on each bonnet intermediate its ends extending around the chambering rotor and nested with a running fit between the inner ends of its helical gears and the helical gears of said main rotor;

the end of said steam duct receiving said knife edge so that steam under pressure delivered thereto is deflected laterally from both sides thereof into the ends of the said expansion chambers;

a steam manifold connected to a source of steam under pressure;

and a plurality of conduits interconnecting said manifold and the respective steam ducts.

2. In the engine of claim 1, each bulkhead and the corresponding steamduct being rectangular in cross section so as to occupy substantially all of the space between said rotor gears.

3. In the steam engine of claim 1, said tang chamfer extending at an angle of about 45-55 on opposite sides of a plane through said knife edge for distributing the flowing steam endwise into the said expansion chambers as they develop progressively at said knife edge on opposite sides thereof.

4. In the steam engine of claim 1, said steam duct being mounted upon said bonnet; and angle members 7 on opposite sides of said steam' duct secured thereto and to said bonnet.

5. In the steam engine of claim 1 said steam manifold being circular and arranged coaxially of said driven shaft.

6. In the steam engine of claim 1, a main gear secured on said driven shaft outwardlyof an end plate; and a pinion secured upon each of said axle shafts and in mesh with said maingear, wherebya synchronized drive relation is established between said chambering rotors and main rotor, the respective helicoid teeth of the opposed main and chambering rotors being loosely assembled during continuous movements in a non-driving relation.

7. In the steam engine of claim 1, said helical gears of the main rotor and the chambering rotors including a spacing collar on and intermediate the ends of said driven shaft and axles, and a plurality of thin flat gear tooth discs on said shaft and axles respectively bearing against said collar, a retaining collar on said shaft and axles retainingly engaging said discs, said discs making up a helicoid being progressively advanced a uniform distance to define the teeth of said helicoid; and a series of spaced fasteners arranged in a circle and extending through apertures in said retaining collar and discs and threaded into said spacing collar, whereby the disc edges are of zig-zag step form in an axial direction.

8. In the steam engine of claim7, the progressive advancing of said discs defining said helicoid being equal to the thickness of said discs approximately.

9. In the steam engine of claim.7, the corresponding arcuate surfaces of said bonnet having a series of spaced grooves and ridges loosely receiving the radial ends of the gear teeth on said gear tooth discs.

10. In the steam engine of claim 7, the gear tooth discs consisting of alternating group 1 and group 2 discs, the group 1 discs having a larger than normal OD. and a smaller than normal root diameter with respect to the pitch circle; said group 2 discs having a smaller than normal OD. and a larger than normal root diameter, whereby the respective gear teeth defining a helical gear element of one rotor have a series of alternately ridges and depressions for respective cooperative registry with a corresponding series of depressions and ridges in the roots of the mating gear element of the opposing rotor.

11. In the steam engine of claim 10, wherein the respective gear teeth roots between adjacent teeth define a helical gear element of one rotor having a series of alternately ridges and depressions for respective cooperative registry with the corresponding depressions and ridges in the mating gear element of the opposing rotor.

12. In the steam engine of claim 10, the corresponding arcuate surfaces of said bonnet having a series of spaced grooves and ridges loosely receiving the respective radial staggered ends of the gear teeth of the registering rotors. =I 

1. In a steam engine, a base; a pair of end plates thereon; a driven shaft spanning and journalled upon said end plates; a main rotor including a pair of spaced helicoid gears of opposite hand mounted on and secured to said shaft; a series of spaced axles spanning and journalled upon said end plates, arranged around, outwardly of and parallel to said shaft; a chambering rotor including a pair of spaced helicoid gears of corresponding opposite hand mounted on and secured to each of said axles; with the spiral gear teeth of each chambering rotor in mesh with the corresponding spiral gear teeth of said main rotor; an elongated bonnet adjacent and parallel to each chambering rotor interposed between and secured to said end plates; said bonnet having a pair of intersecting elongated transversely arcuate surfaces adjacent said rotors providing a close running fit with the peripheries of both mating rotors throughout their length and extending circumferentially both sides of a central longitudinal plane wherein the peripheries of both rotors coincide, thence through arcs equal to those spanned by the helixes of each rotor; each bonnet sealing off the respective expansion chambers defined between and along the adjacent intermeshing chambering rotors and main rotor; an arcuate bulkhead projecting outwardly of each bonnet arcuate surface intermediate its ends nested with a running fit within the annular space between the inner ends of the helical gears of the chambering rotor and main rotor, closing off the corresponding expansion chambers on opposite sides of the bulkhead; said bulkheads merging at one end and terminating in a tang, chamferred upon its opposite sides defining a knife edge; an arcuate steam duct mounted on each bonnet intermediate its ends extending around the chambering rotor and nested with a running fit between the inner ends of its helical gears and the helical gears of said main rotor; the end of said steam duct receiving said knife edge so that steam under pressure delivered thereto is deflected laterally from both sides thereof into the ends of the said expansion chambers; a steam manifold connected to a source of steam under pressure; and a plurality of conduits interconnecting said manifold and the respective steam ducts.
 2. In the engine of claim 1, each bulkhead and the corresponding steamduct being rectangular in cross section so as to occupy substantially all of the space between said rotor gears.
 3. In the steam engine of claim 1, said tang chamfer extending at an angle of about 45*-55* on opposite sides of a plane through said knife edge for distributing the flowing steam endwise into the said expansion chambers as they develop progressively at said knife edge on opposite sides thereof.
 4. In the steam engine of claim 1, said steam duct being mounted upon said bonnet; and angle members on opposite sides of said steam duct secured thereto and to said bonnet.
 5. In the steam engine of claim 1, said steam manifold being circular and arranged coaxially of said driven shaft.
 6. In the steam engine of claim 1, a main gear secured on said driven shaft outwardly of an end plate; and a pinion secured upon each of said axle shafts and in mesh with said main gear, whereby a synchronized drive relation is established between said chambering rotors and main rotor, the respective helicoid teeth of the opposed main and chambering rotors being loosely assembled during continuous movements in a non-driving relation.
 7. In the steam engine of claim 1, said helical gears of the main rotor and the chambering rotors including a spacing collar on and intermediate the ends of said driven shaft and axles, and a plurality of thin flat gear tooth discs on said shaft and axles respectively bearing against said collar, a retaining collar on said shaft and axles retainingly engaging said discs, said discs making up a helicoid being progressively advanced a uniform distance to define the teeth of said helicoid; and a series of spaced fasteners arranged in a circle and extending through apertures in said retaining collar and discs and threaded into said spacing collar, whereby the disc edges are of zig-zag step form in an axial direction.
 8. In the steam engine of claim 7, the progressive advancing of said discs defining said helicoid being equal to the thickness of said discs approximately.
 9. In the steam engine of claim 7, the corresponding arcuate surfaces of said bonnet having a series of spaced grooves and ridges loosely receiving the radial ends of the gear teeth on said gear tooth discs.
 10. In the steam engine of claim 7, the gear tooth discs consisting of alternating group 1 and group 2 discs, the group 1 discs having a larger than normal O.D. and a smaller than normal root diameter with respect to the pitch circle; said group 2 discs having a smaller than normal O.D. and a larger than normal root diameter, whereby the respective gear teeth defining a helical gear Element of one rotor have a series of alternately ridges and depressions for respective cooperative registry with a corresponding series of depressions and ridges in the roots of the mating gear element of the opposing rotor.
 11. In the steam engine of claim 10, wherein the respective gear teeth roots between adjacent teeth define a helical gear element of one rotor having a series of alternately ridges and depressions for respective cooperative registry with the corresponding depressions and ridges in the mating gear element of the opposing rotor.
 12. In the steam engine of claim 10, the corresponding arcuate surfaces of said bonnet having a series of spaced grooves and ridges loosely receiving the respective radial staggered ends of the gear teeth of the registering rotors. 